Relay stations (hereinafter “RS”) are added to wireless communication networks to increase the coverage range, user data rates, or both, at the periphery of the cellular coverage area. A multi-hop network facilities communication occurs between a base station (hereinafter “BS”) and subscriber stations (also referred to as mobile stations, “MS”) in the extended coverage area provided by a relay station. In a multi-hop network, a signal from a source may reach its destination in multiple hops through the use of the Relay stations. Relay stations typically boost the downlink (base station to the subscriber station) and uplink (subscriber station to the base station) signals regardless of whether the relay station is a fixed relay station (hereinafter “RS”) or a mobile relay station. Current systems fail to effectively increase relay system coverage while employing power saving mechanisms for the relay station. Moreover, no procedures are currently available for effectively managing load conditions, such as the number of received and transmitted data and acknowledgment packets.
In MIMO systems, each of a plurality of data streams is individually encoded and modulated before being transmitted by different physical antennas or effective antennas. The combined data streams are then received at multiple antennas of a receiver. At the receiver, each data stream is separated and extracted from the combined signal. This process is generally performed using a minimum mean squared error (MMSE) or MMSE-successive interference cancellation (SIC) algorithm.
The MMSE-SIC algorithm detects signal components or data streams one at a time by repeatedly applying the MMSE algorithm. After one signal component is extracted, the data stream passes through a virtual channel for that data stream and is then subtracted or cancelled from the combined signal. Therefore, for each subsequent application of MMSE, the dimension of the underlying system is reduced by one. This process is called successive interference cancellation since each detected data stream acts as interference for the detection of the remaining data streams.
The order in which the successive interference cancellation is performed on the data streams has an enormous impact on the performance of MMSE-SIC. However, in typical MIMO systems, the order is randomly determined or pre-determined without regard for the actual system conditions. As a result, a stream that is inaccurately decoded and then reconstructed and canceled from the combined signal will introduce errors into the combined signal for the remaining data streams. One solution to this problem involves searching for all possible cancellation orders by verifying the accuracy of the decoded data streams before reconstruction and cancellation. However, because searching for all possible cancellation orders requires a large number of decoding attempts, this approach results in an extremely complex receiver.
Therefore, there is a need in the art for an improved relay station. In particular, there is a need for a system to more effectively and efficiently manage and decode data packets in a multi-hop network.